1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/kernel.h> 44 #include <sys/lock.h> 45 #include <sys/mbuf.h> 46 #include <sys/mutex.h> 47 #include <sys/protosw.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/sysctl.h> 51 #include <sys/vimage.h> 52 53 #include <net/if.h> 54 #include <net/route.h> 55 56 #include <netinet/in.h> 57 #include <netinet/in_systm.h> 58 #include <netinet/ip.h> 59 #include <netinet/in_pcb.h> 60 #include <netinet/ip_var.h> 61 #include <netinet/ip_options.h> 62 #ifdef INET6 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #endif 67 #include <netinet/tcp.h> 68 #define TCPOUTFLAGS 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcpip.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcp_debug.h> 76 #endif 77 #include <netinet/vinet.h> 78 79 #ifdef IPSEC 80 #include <netipsec/ipsec.h> 81 #endif /*IPSEC*/ 82 83 #include <machine/in_cksum.h> 84 85 #include <security/mac/mac_framework.h> 86 87 #ifdef notyet 88 extern struct mbuf *m_copypack(); 89 #endif 90 91 #ifdef VIMAGE_GLOBALS 92 int path_mtu_discovery; 93 int ss_fltsz; 94 int ss_fltsz_local; 95 int tcp_do_newreno; 96 int tcp_do_tso; 97 int tcp_do_autosndbuf; 98 int tcp_autosndbuf_inc; 99 int tcp_autosndbuf_max; 100 #endif 101 102 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, path_mtu_discovery, 103 CTLFLAG_RW, path_mtu_discovery, 1, "Enable Path MTU Discovery"); 104 105 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, 106 slowstart_flightsize, CTLFLAG_RW, 107 ss_fltsz, 1, "Slow start flight size"); 108 109 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, 110 local_slowstart_flightsize, CTLFLAG_RW, 111 ss_fltsz_local, 1, "Slow start flight size for local networks"); 112 113 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 114 tcp_do_newreno, 0, "Enable NewReno Algorithms"); 115 116 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 117 tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 118 119 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_auto, 120 CTLFLAG_RW, 121 tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 122 123 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_inc, 124 CTLFLAG_RW, tcp_autosndbuf_inc, 0, 125 "Incrementor step size of automatic send buffer"); 126 127 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_max, 128 CTLFLAG_RW, tcp_autosndbuf_max, 0, 129 "Max size of automatic send buffer"); 130 131 132 /* 133 * Tcp output routine: figure out what should be sent and send it. 134 */ 135 int 136 tcp_output(struct tcpcb *tp) 137 { 138 INIT_VNET_INET(tp->t_inpcb->inp_vnet); 139 struct socket *so = tp->t_inpcb->inp_socket; 140 long len, recwin, sendwin; 141 int off, flags, error; 142 struct mbuf *m; 143 struct ip *ip = NULL; 144 struct ipovly *ipov = NULL; 145 struct tcphdr *th; 146 u_char opt[TCP_MAXOLEN]; 147 unsigned ipoptlen, optlen, hdrlen; 148 #ifdef IPSEC 149 unsigned ipsec_optlen = 0; 150 #endif 151 int idle, sendalot; 152 int sack_rxmit, sack_bytes_rxmt; 153 struct sackhole *p; 154 int tso = 0; 155 struct tcpopt to; 156 #if 0 157 int maxburst = TCP_MAXBURST; 158 #endif 159 #ifdef INET6 160 struct ip6_hdr *ip6 = NULL; 161 int isipv6; 162 163 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 164 #endif 165 166 INP_WLOCK_ASSERT(tp->t_inpcb); 167 168 /* 169 * Determine length of data that should be transmitted, 170 * and flags that will be used. 171 * If there is some data or critical controls (SYN, RST) 172 * to send, then transmit; otherwise, investigate further. 173 */ 174 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 175 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) { 176 /* 177 * We have been idle for "a while" and no acks are 178 * expected to clock out any data we send -- 179 * slow start to get ack "clock" running again. 180 * 181 * Set the slow-start flight size depending on whether 182 * this is a local network or not. 183 */ 184 int ss = V_ss_fltsz; 185 #ifdef INET6 186 if (isipv6) { 187 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 188 ss = V_ss_fltsz_local; 189 } else 190 #endif /* INET6 */ 191 if (in_localaddr(tp->t_inpcb->inp_faddr)) 192 ss = V_ss_fltsz_local; 193 tp->snd_cwnd = tp->t_maxseg * ss; 194 } 195 tp->t_flags &= ~TF_LASTIDLE; 196 if (idle) { 197 if (tp->t_flags & TF_MORETOCOME) { 198 tp->t_flags |= TF_LASTIDLE; 199 idle = 0; 200 } 201 } 202 again: 203 /* 204 * If we've recently taken a timeout, snd_max will be greater than 205 * snd_nxt. There may be SACK information that allows us to avoid 206 * resending already delivered data. Adjust snd_nxt accordingly. 207 */ 208 if ((tp->t_flags & TF_SACK_PERMIT) && 209 SEQ_LT(tp->snd_nxt, tp->snd_max)) 210 tcp_sack_adjust(tp); 211 sendalot = 0; 212 off = tp->snd_nxt - tp->snd_una; 213 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 214 sendwin = min(sendwin, tp->snd_bwnd); 215 216 flags = tcp_outflags[tp->t_state]; 217 /* 218 * Send any SACK-generated retransmissions. If we're explicitly trying 219 * to send out new data (when sendalot is 1), bypass this function. 220 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 221 * we're replacing a (future) new transmission with a retransmission 222 * now, and we previously incremented snd_cwnd in tcp_input(). 223 */ 224 /* 225 * Still in sack recovery , reset rxmit flag to zero. 226 */ 227 sack_rxmit = 0; 228 sack_bytes_rxmt = 0; 229 len = 0; 230 p = NULL; 231 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 232 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 233 long cwin; 234 235 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 236 if (cwin < 0) 237 cwin = 0; 238 /* Do not retransmit SACK segments beyond snd_recover */ 239 if (SEQ_GT(p->end, tp->snd_recover)) { 240 /* 241 * (At least) part of sack hole extends beyond 242 * snd_recover. Check to see if we can rexmit data 243 * for this hole. 244 */ 245 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 246 /* 247 * Can't rexmit any more data for this hole. 248 * That data will be rexmitted in the next 249 * sack recovery episode, when snd_recover 250 * moves past p->rxmit. 251 */ 252 p = NULL; 253 goto after_sack_rexmit; 254 } else 255 /* Can rexmit part of the current hole */ 256 len = ((long)ulmin(cwin, 257 tp->snd_recover - p->rxmit)); 258 } else 259 len = ((long)ulmin(cwin, p->end - p->rxmit)); 260 off = p->rxmit - tp->snd_una; 261 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 262 __func__, off)); 263 if (len > 0) { 264 sack_rxmit = 1; 265 sendalot = 1; 266 TCPSTAT_INC(tcps_sack_rexmits); 267 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 268 min(len, tp->t_maxseg)); 269 } 270 } 271 after_sack_rexmit: 272 /* 273 * Get standard flags, and add SYN or FIN if requested by 'hidden' 274 * state flags. 275 */ 276 if (tp->t_flags & TF_NEEDFIN) 277 flags |= TH_FIN; 278 if (tp->t_flags & TF_NEEDSYN) 279 flags |= TH_SYN; 280 281 SOCKBUF_LOCK(&so->so_snd); 282 /* 283 * If in persist timeout with window of 0, send 1 byte. 284 * Otherwise, if window is small but nonzero 285 * and timer expired, we will send what we can 286 * and go to transmit state. 287 */ 288 if (tp->t_flags & TF_FORCEDATA) { 289 if (sendwin == 0) { 290 /* 291 * If we still have some data to send, then 292 * clear the FIN bit. Usually this would 293 * happen below when it realizes that we 294 * aren't sending all the data. However, 295 * if we have exactly 1 byte of unsent data, 296 * then it won't clear the FIN bit below, 297 * and if we are in persist state, we wind 298 * up sending the packet without recording 299 * that we sent the FIN bit. 300 * 301 * We can't just blindly clear the FIN bit, 302 * because if we don't have any more data 303 * to send then the probe will be the FIN 304 * itself. 305 */ 306 if (off < so->so_snd.sb_cc) 307 flags &= ~TH_FIN; 308 sendwin = 1; 309 } else { 310 tcp_timer_activate(tp, TT_PERSIST, 0); 311 tp->t_rxtshift = 0; 312 } 313 } 314 315 /* 316 * If snd_nxt == snd_max and we have transmitted a FIN, the 317 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 318 * a negative length. This can also occur when TCP opens up 319 * its congestion window while receiving additional duplicate 320 * acks after fast-retransmit because TCP will reset snd_nxt 321 * to snd_max after the fast-retransmit. 322 * 323 * In the normal retransmit-FIN-only case, however, snd_nxt will 324 * be set to snd_una, the offset will be 0, and the length may 325 * wind up 0. 326 * 327 * If sack_rxmit is true we are retransmitting from the scoreboard 328 * in which case len is already set. 329 */ 330 if (sack_rxmit == 0) { 331 if (sack_bytes_rxmt == 0) 332 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 333 else { 334 long cwin; 335 336 /* 337 * We are inside of a SACK recovery episode and are 338 * sending new data, having retransmitted all the 339 * data possible in the scoreboard. 340 */ 341 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 342 - off); 343 /* 344 * Don't remove this (len > 0) check ! 345 * We explicitly check for len > 0 here (although it 346 * isn't really necessary), to work around a gcc 347 * optimization issue - to force gcc to compute 348 * len above. Without this check, the computation 349 * of len is bungled by the optimizer. 350 */ 351 if (len > 0) { 352 cwin = tp->snd_cwnd - 353 (tp->snd_nxt - tp->sack_newdata) - 354 sack_bytes_rxmt; 355 if (cwin < 0) 356 cwin = 0; 357 len = lmin(len, cwin); 358 } 359 } 360 } 361 362 /* 363 * Lop off SYN bit if it has already been sent. However, if this 364 * is SYN-SENT state and if segment contains data and if we don't 365 * know that foreign host supports TAO, suppress sending segment. 366 */ 367 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 368 if (tp->t_state != TCPS_SYN_RECEIVED) 369 flags &= ~TH_SYN; 370 off--, len++; 371 } 372 373 /* 374 * Be careful not to send data and/or FIN on SYN segments. 375 * This measure is needed to prevent interoperability problems 376 * with not fully conformant TCP implementations. 377 */ 378 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 379 len = 0; 380 flags &= ~TH_FIN; 381 } 382 383 if (len < 0) { 384 /* 385 * If FIN has been sent but not acked, 386 * but we haven't been called to retransmit, 387 * len will be < 0. Otherwise, window shrank 388 * after we sent into it. If window shrank to 0, 389 * cancel pending retransmit, pull snd_nxt back 390 * to (closed) window, and set the persist timer 391 * if it isn't already going. If the window didn't 392 * close completely, just wait for an ACK. 393 */ 394 len = 0; 395 if (sendwin == 0) { 396 tcp_timer_activate(tp, TT_REXMT, 0); 397 tp->t_rxtshift = 0; 398 tp->snd_nxt = tp->snd_una; 399 if (!tcp_timer_active(tp, TT_PERSIST)) 400 tcp_setpersist(tp); 401 } 402 } 403 404 /* len will be >= 0 after this point. */ 405 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 406 407 /* 408 * Automatic sizing of send socket buffer. Often the send buffer 409 * size is not optimally adjusted to the actual network conditions 410 * at hand (delay bandwidth product). Setting the buffer size too 411 * small limits throughput on links with high bandwidth and high 412 * delay (eg. trans-continental/oceanic links). Setting the 413 * buffer size too big consumes too much real kernel memory, 414 * especially with many connections on busy servers. 415 * 416 * The criteria to step up the send buffer one notch are: 417 * 1. receive window of remote host is larger than send buffer 418 * (with a fudge factor of 5/4th); 419 * 2. send buffer is filled to 7/8th with data (so we actually 420 * have data to make use of it); 421 * 3. send buffer fill has not hit maximal automatic size; 422 * 4. our send window (slow start and cogestion controlled) is 423 * larger than sent but unacknowledged data in send buffer. 424 * 425 * The remote host receive window scaling factor may limit the 426 * growing of the send buffer before it reaches its allowed 427 * maximum. 428 * 429 * It scales directly with slow start or congestion window 430 * and does at most one step per received ACK. This fast 431 * scaling has the drawback of growing the send buffer beyond 432 * what is strictly necessary to make full use of a given 433 * delay*bandwith product. However testing has shown this not 434 * to be much of an problem. At worst we are trading wasting 435 * of available bandwith (the non-use of it) for wasting some 436 * socket buffer memory. 437 * 438 * TODO: Shrink send buffer during idle periods together 439 * with congestion window. Requires another timer. Has to 440 * wait for upcoming tcp timer rewrite. 441 */ 442 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 443 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 444 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 445 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 446 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 447 if (!sbreserve_locked(&so->so_snd, 448 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 449 V_tcp_autosndbuf_max), so, curthread)) 450 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 451 } 452 } 453 454 /* 455 * Truncate to the maximum segment length or enable TCP Segmentation 456 * Offloading (if supported by hardware) and ensure that FIN is removed 457 * if the length no longer contains the last data byte. 458 * 459 * TSO may only be used if we are in a pure bulk sending state. The 460 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 461 * IP options prevent using TSO. With TSO the TCP header is the same 462 * (except for the sequence number) for all generated packets. This 463 * makes it impossible to transmit any options which vary per generated 464 * segment or packet. 465 * 466 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 467 * removal of FIN (if not already catched here) are handled later after 468 * the exact length of the TCP options are known. 469 */ 470 #ifdef IPSEC 471 /* 472 * Pre-calculate here as we save another lookup into the darknesses 473 * of IPsec that way and can actually decide if TSO is ok. 474 */ 475 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 476 #endif 477 if (len > tp->t_maxseg) { 478 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 479 ((tp->t_flags & TF_SIGNATURE) == 0) && 480 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 481 tp->t_inpcb->inp_options == NULL && 482 tp->t_inpcb->in6p_options == NULL 483 #ifdef IPSEC 484 && ipsec_optlen == 0 485 #endif 486 ) { 487 tso = 1; 488 } else { 489 len = tp->t_maxseg; 490 sendalot = 1; 491 tso = 0; 492 } 493 } 494 if (sack_rxmit) { 495 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 496 flags &= ~TH_FIN; 497 } else { 498 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 499 flags &= ~TH_FIN; 500 } 501 502 recwin = sbspace(&so->so_rcv); 503 504 /* 505 * Sender silly window avoidance. We transmit under the following 506 * conditions when len is non-zero: 507 * 508 * - We have a full segment (or more with TSO) 509 * - This is the last buffer in a write()/send() and we are 510 * either idle or running NODELAY 511 * - we've timed out (e.g. persist timer) 512 * - we have more then 1/2 the maximum send window's worth of 513 * data (receiver may be limited the window size) 514 * - we need to retransmit 515 */ 516 if (len) { 517 if (len >= tp->t_maxseg) 518 goto send; 519 /* 520 * NOTE! on localhost connections an 'ack' from the remote 521 * end may occur synchronously with the output and cause 522 * us to flush a buffer queued with moretocome. XXX 523 * 524 * note: the len + off check is almost certainly unnecessary. 525 */ 526 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 527 (idle || (tp->t_flags & TF_NODELAY)) && 528 len + off >= so->so_snd.sb_cc && 529 (tp->t_flags & TF_NOPUSH) == 0) { 530 goto send; 531 } 532 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 533 goto send; 534 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 535 goto send; 536 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 537 goto send; 538 if (sack_rxmit) 539 goto send; 540 } 541 542 /* 543 * Compare available window to amount of window 544 * known to peer (as advertised window less 545 * next expected input). If the difference is at least two 546 * max size segments, or at least 50% of the maximum possible 547 * window, then want to send a window update to peer. 548 * Skip this if the connection is in T/TCP half-open state. 549 * Don't send pure window updates when the peer has closed 550 * the connection and won't ever send more data. 551 */ 552 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 553 !TCPS_HAVERCVDFIN(tp->t_state)) { 554 /* 555 * "adv" is the amount we can increase the window, 556 * taking into account that we are limited by 557 * TCP_MAXWIN << tp->rcv_scale. 558 */ 559 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 560 (tp->rcv_adv - tp->rcv_nxt); 561 562 if (adv >= (long) (2 * tp->t_maxseg)) 563 goto send; 564 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 565 goto send; 566 } 567 568 /* 569 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 570 * is also a catch-all for the retransmit timer timeout case. 571 */ 572 if (tp->t_flags & TF_ACKNOW) 573 goto send; 574 if ((flags & TH_RST) || 575 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 576 goto send; 577 if (SEQ_GT(tp->snd_up, tp->snd_una)) 578 goto send; 579 /* 580 * If our state indicates that FIN should be sent 581 * and we have not yet done so, then we need to send. 582 */ 583 if (flags & TH_FIN && 584 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 585 goto send; 586 /* 587 * In SACK, it is possible for tcp_output to fail to send a segment 588 * after the retransmission timer has been turned off. Make sure 589 * that the retransmission timer is set. 590 */ 591 if ((tp->t_flags & TF_SACK_PERMIT) && 592 SEQ_GT(tp->snd_max, tp->snd_una) && 593 !tcp_timer_active(tp, TT_REXMT) && 594 !tcp_timer_active(tp, TT_PERSIST)) { 595 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 596 goto just_return; 597 } 598 /* 599 * TCP window updates are not reliable, rather a polling protocol 600 * using ``persist'' packets is used to insure receipt of window 601 * updates. The three ``states'' for the output side are: 602 * idle not doing retransmits or persists 603 * persisting to move a small or zero window 604 * (re)transmitting and thereby not persisting 605 * 606 * tcp_timer_active(tp, TT_PERSIST) 607 * is true when we are in persist state. 608 * (tp->t_flags & TF_FORCEDATA) 609 * is set when we are called to send a persist packet. 610 * tcp_timer_active(tp, TT_REXMT) 611 * is set when we are retransmitting 612 * The output side is idle when both timers are zero. 613 * 614 * If send window is too small, there is data to transmit, and no 615 * retransmit or persist is pending, then go to persist state. 616 * If nothing happens soon, send when timer expires: 617 * if window is nonzero, transmit what we can, 618 * otherwise force out a byte. 619 */ 620 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 621 !tcp_timer_active(tp, TT_PERSIST)) { 622 tp->t_rxtshift = 0; 623 tcp_setpersist(tp); 624 } 625 626 /* 627 * No reason to send a segment, just return. 628 */ 629 just_return: 630 SOCKBUF_UNLOCK(&so->so_snd); 631 return (0); 632 633 send: 634 SOCKBUF_LOCK_ASSERT(&so->so_snd); 635 /* 636 * Before ESTABLISHED, force sending of initial options 637 * unless TCP set not to do any options. 638 * NOTE: we assume that the IP/TCP header plus TCP options 639 * always fit in a single mbuf, leaving room for a maximum 640 * link header, i.e. 641 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 642 */ 643 optlen = 0; 644 #ifdef INET6 645 if (isipv6) 646 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 647 else 648 #endif 649 hdrlen = sizeof (struct tcpiphdr); 650 651 /* 652 * Compute options for segment. 653 * We only have to care about SYN and established connection 654 * segments. Options for SYN-ACK segments are handled in TCP 655 * syncache. 656 */ 657 if ((tp->t_flags & TF_NOOPT) == 0) { 658 to.to_flags = 0; 659 /* Maximum segment size. */ 660 if (flags & TH_SYN) { 661 tp->snd_nxt = tp->iss; 662 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 663 to.to_flags |= TOF_MSS; 664 } 665 /* Window scaling. */ 666 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 667 to.to_wscale = tp->request_r_scale; 668 to.to_flags |= TOF_SCALE; 669 } 670 /* Timestamps. */ 671 if ((tp->t_flags & TF_RCVD_TSTMP) || 672 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 673 to.to_tsval = ticks + tp->ts_offset; 674 to.to_tsecr = tp->ts_recent; 675 to.to_flags |= TOF_TS; 676 /* Set receive buffer autosizing timestamp. */ 677 if (tp->rfbuf_ts == 0 && 678 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 679 tp->rfbuf_ts = ticks; 680 } 681 /* Selective ACK's. */ 682 if (tp->t_flags & TF_SACK_PERMIT) { 683 if (flags & TH_SYN) 684 to.to_flags |= TOF_SACKPERM; 685 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 686 (tp->t_flags & TF_SACK_PERMIT) && 687 tp->rcv_numsacks > 0) { 688 to.to_flags |= TOF_SACK; 689 to.to_nsacks = tp->rcv_numsacks; 690 to.to_sacks = (u_char *)tp->sackblks; 691 } 692 } 693 #ifdef TCP_SIGNATURE 694 /* TCP-MD5 (RFC2385). */ 695 if (tp->t_flags & TF_SIGNATURE) 696 to.to_flags |= TOF_SIGNATURE; 697 #endif /* TCP_SIGNATURE */ 698 699 /* Processing the options. */ 700 hdrlen += optlen = tcp_addoptions(&to, opt); 701 } 702 703 #ifdef INET6 704 if (isipv6) 705 ipoptlen = ip6_optlen(tp->t_inpcb); 706 else 707 #endif 708 if (tp->t_inpcb->inp_options) 709 ipoptlen = tp->t_inpcb->inp_options->m_len - 710 offsetof(struct ipoption, ipopt_list); 711 else 712 ipoptlen = 0; 713 #ifdef IPSEC 714 ipoptlen += ipsec_optlen; 715 #endif 716 717 /* 718 * Adjust data length if insertion of options will 719 * bump the packet length beyond the t_maxopd length. 720 * Clear the FIN bit because we cut off the tail of 721 * the segment. 722 * 723 * When doing TSO limit a burst to TCP_MAXWIN minus the 724 * IP, TCP and Options length to keep ip->ip_len from 725 * overflowing. Prevent the last segment from being 726 * fractional thus making them all equal sized and set 727 * the flag to continue sending. TSO is disabled when 728 * IP options or IPSEC are present. 729 */ 730 if (len + optlen + ipoptlen > tp->t_maxopd) { 731 flags &= ~TH_FIN; 732 if (tso) { 733 if (len > TCP_MAXWIN - hdrlen - optlen) { 734 len = TCP_MAXWIN - hdrlen - optlen; 735 len = len - (len % (tp->t_maxopd - optlen)); 736 sendalot = 1; 737 } else if (tp->t_flags & TF_NEEDFIN) 738 sendalot = 1; 739 } else { 740 len = tp->t_maxopd - optlen - ipoptlen; 741 sendalot = 1; 742 } 743 } 744 745 /*#ifdef DIAGNOSTIC*/ 746 #ifdef INET6 747 if (max_linkhdr + hdrlen > MCLBYTES) 748 #else 749 if (max_linkhdr + hdrlen > MHLEN) 750 #endif 751 panic("tcphdr too big"); 752 /*#endif*/ 753 754 /* 755 * This KASSERT is here to catch edge cases at a well defined place. 756 * Before, those had triggered (random) panic conditions further down. 757 */ 758 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 759 760 /* 761 * Grab a header mbuf, attaching a copy of data to 762 * be transmitted, and initialize the header from 763 * the template for sends on this connection. 764 */ 765 if (len) { 766 struct mbuf *mb; 767 u_int moff; 768 769 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 770 TCPSTAT_INC(tcps_sndprobe); 771 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 772 TCPSTAT_INC(tcps_sndrexmitpack); 773 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 774 } else { 775 TCPSTAT_INC(tcps_sndpack); 776 TCPSTAT_ADD(tcps_sndbyte, len); 777 } 778 #ifdef notyet 779 if ((m = m_copypack(so->so_snd.sb_mb, off, 780 (int)len, max_linkhdr + hdrlen)) == 0) { 781 SOCKBUF_UNLOCK(&so->so_snd); 782 error = ENOBUFS; 783 goto out; 784 } 785 /* 786 * m_copypack left space for our hdr; use it. 787 */ 788 m->m_len += hdrlen; 789 m->m_data -= hdrlen; 790 #else 791 MGETHDR(m, M_DONTWAIT, MT_DATA); 792 if (m == NULL) { 793 SOCKBUF_UNLOCK(&so->so_snd); 794 error = ENOBUFS; 795 goto out; 796 } 797 #ifdef INET6 798 if (MHLEN < hdrlen + max_linkhdr) { 799 MCLGET(m, M_DONTWAIT); 800 if ((m->m_flags & M_EXT) == 0) { 801 SOCKBUF_UNLOCK(&so->so_snd); 802 m_freem(m); 803 error = ENOBUFS; 804 goto out; 805 } 806 } 807 #endif 808 m->m_data += max_linkhdr; 809 m->m_len = hdrlen; 810 811 /* 812 * Start the m_copy functions from the closest mbuf 813 * to the offset in the socket buffer chain. 814 */ 815 mb = sbsndptr(&so->so_snd, off, len, &moff); 816 817 if (len <= MHLEN - hdrlen - max_linkhdr) { 818 m_copydata(mb, moff, (int)len, 819 mtod(m, caddr_t) + hdrlen); 820 m->m_len += len; 821 } else { 822 m->m_next = m_copy(mb, moff, (int)len); 823 if (m->m_next == NULL) { 824 SOCKBUF_UNLOCK(&so->so_snd); 825 (void) m_free(m); 826 error = ENOBUFS; 827 goto out; 828 } 829 } 830 #endif 831 /* 832 * If we're sending everything we've got, set PUSH. 833 * (This will keep happy those implementations which only 834 * give data to the user when a buffer fills or 835 * a PUSH comes in.) 836 */ 837 if (off + len == so->so_snd.sb_cc) 838 flags |= TH_PUSH; 839 SOCKBUF_UNLOCK(&so->so_snd); 840 } else { 841 SOCKBUF_UNLOCK(&so->so_snd); 842 if (tp->t_flags & TF_ACKNOW) 843 TCPSTAT_INC(tcps_sndacks); 844 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 845 TCPSTAT_INC(tcps_sndctrl); 846 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 847 TCPSTAT_INC(tcps_sndurg); 848 else 849 TCPSTAT_INC(tcps_sndwinup); 850 851 MGETHDR(m, M_DONTWAIT, MT_DATA); 852 if (m == NULL) { 853 error = ENOBUFS; 854 goto out; 855 } 856 #ifdef INET6 857 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 858 MHLEN >= hdrlen) { 859 MH_ALIGN(m, hdrlen); 860 } else 861 #endif 862 m->m_data += max_linkhdr; 863 m->m_len = hdrlen; 864 } 865 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 866 m->m_pkthdr.rcvif = (struct ifnet *)0; 867 #ifdef MAC 868 mac_inpcb_create_mbuf(tp->t_inpcb, m); 869 #endif 870 #ifdef INET6 871 if (isipv6) { 872 ip6 = mtod(m, struct ip6_hdr *); 873 th = (struct tcphdr *)(ip6 + 1); 874 tcpip_fillheaders(tp->t_inpcb, ip6, th); 875 } else 876 #endif /* INET6 */ 877 { 878 ip = mtod(m, struct ip *); 879 ipov = (struct ipovly *)ip; 880 th = (struct tcphdr *)(ip + 1); 881 tcpip_fillheaders(tp->t_inpcb, ip, th); 882 } 883 884 /* 885 * Fill in fields, remembering maximum advertised 886 * window for use in delaying messages about window sizes. 887 * If resending a FIN, be sure not to use a new sequence number. 888 */ 889 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 890 tp->snd_nxt == tp->snd_max) 891 tp->snd_nxt--; 892 /* 893 * If we are starting a connection, send ECN setup 894 * SYN packet. If we are on a retransmit, we may 895 * resend those bits a number of times as per 896 * RFC 3168. 897 */ 898 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 899 if (tp->t_rxtshift >= 1) { 900 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 901 flags |= TH_ECE|TH_CWR; 902 } else 903 flags |= TH_ECE|TH_CWR; 904 } 905 906 if (tp->t_state == TCPS_ESTABLISHED && 907 (tp->t_flags & TF_ECN_PERMIT)) { 908 /* 909 * If the peer has ECN, mark data packets with 910 * ECN capable transmission (ECT). 911 * Ignore pure ack packets, retransmissions and window probes. 912 */ 913 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 914 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 915 #ifdef INET6 916 if (isipv6) 917 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 918 else 919 #endif 920 ip->ip_tos |= IPTOS_ECN_ECT0; 921 TCPSTAT_INC(tcps_ecn_ect0); 922 } 923 924 /* 925 * Reply with proper ECN notifications. 926 */ 927 if (tp->t_flags & TF_ECN_SND_CWR) { 928 flags |= TH_CWR; 929 tp->t_flags &= ~TF_ECN_SND_CWR; 930 } 931 if (tp->t_flags & TF_ECN_SND_ECE) 932 flags |= TH_ECE; 933 } 934 935 /* 936 * If we are doing retransmissions, then snd_nxt will 937 * not reflect the first unsent octet. For ACK only 938 * packets, we do not want the sequence number of the 939 * retransmitted packet, we want the sequence number 940 * of the next unsent octet. So, if there is no data 941 * (and no SYN or FIN), use snd_max instead of snd_nxt 942 * when filling in ti_seq. But if we are in persist 943 * state, snd_max might reflect one byte beyond the 944 * right edge of the window, so use snd_nxt in that 945 * case, since we know we aren't doing a retransmission. 946 * (retransmit and persist are mutually exclusive...) 947 */ 948 if (sack_rxmit == 0) { 949 if (len || (flags & (TH_SYN|TH_FIN)) || 950 tcp_timer_active(tp, TT_PERSIST)) 951 th->th_seq = htonl(tp->snd_nxt); 952 else 953 th->th_seq = htonl(tp->snd_max); 954 } else { 955 th->th_seq = htonl(p->rxmit); 956 p->rxmit += len; 957 tp->sackhint.sack_bytes_rexmit += len; 958 } 959 th->th_ack = htonl(tp->rcv_nxt); 960 if (optlen) { 961 bcopy(opt, th + 1, optlen); 962 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 963 } 964 th->th_flags = flags; 965 /* 966 * Calculate receive window. Don't shrink window, 967 * but avoid silly window syndrome. 968 */ 969 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 970 recwin < (long)tp->t_maxseg) 971 recwin = 0; 972 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 973 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 974 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 975 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 976 977 /* 978 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 979 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 980 * case is handled in syncache. 981 */ 982 if (flags & TH_SYN) 983 th->th_win = htons((u_short) 984 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 985 else 986 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 987 988 /* 989 * Adjust the RXWIN0SENT flag - indicate that we have advertised 990 * a 0 window. This may cause the remote transmitter to stall. This 991 * flag tells soreceive() to disable delayed acknowledgements when 992 * draining the buffer. This can occur if the receiver is attempting 993 * to read more data than can be buffered prior to transmitting on 994 * the connection. 995 */ 996 if (recwin == 0) 997 tp->t_flags |= TF_RXWIN0SENT; 998 else 999 tp->t_flags &= ~TF_RXWIN0SENT; 1000 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1001 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1002 th->th_flags |= TH_URG; 1003 } else 1004 /* 1005 * If no urgent pointer to send, then we pull 1006 * the urgent pointer to the left edge of the send window 1007 * so that it doesn't drift into the send window on sequence 1008 * number wraparound. 1009 */ 1010 tp->snd_up = tp->snd_una; /* drag it along */ 1011 1012 #ifdef TCP_SIGNATURE 1013 if (tp->t_flags & TF_SIGNATURE) { 1014 int sigoff = to.to_signature - opt; 1015 tcp_signature_compute(m, 0, len, optlen, 1016 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1017 } 1018 #endif 1019 1020 /* 1021 * Put TCP length in extended header, and then 1022 * checksum extended header and data. 1023 */ 1024 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1025 #ifdef INET6 1026 if (isipv6) 1027 /* 1028 * ip6_plen is not need to be filled now, and will be filled 1029 * in ip6_output. 1030 */ 1031 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1032 sizeof(struct tcphdr) + optlen + len); 1033 else 1034 #endif /* INET6 */ 1035 { 1036 m->m_pkthdr.csum_flags = CSUM_TCP; 1037 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1038 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1039 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1040 1041 /* IP version must be set here for ipv4/ipv6 checking later */ 1042 KASSERT(ip->ip_v == IPVERSION, 1043 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1044 } 1045 1046 /* 1047 * Enable TSO and specify the size of the segments. 1048 * The TCP pseudo header checksum is always provided. 1049 * XXX: Fixme: This is currently not the case for IPv6. 1050 */ 1051 if (tso) { 1052 m->m_pkthdr.csum_flags = CSUM_TSO; 1053 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1054 } 1055 1056 /* 1057 * In transmit state, time the transmission and arrange for 1058 * the retransmit. In persist state, just set snd_max. 1059 */ 1060 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1061 !tcp_timer_active(tp, TT_PERSIST)) { 1062 tcp_seq startseq = tp->snd_nxt; 1063 1064 /* 1065 * Advance snd_nxt over sequence space of this segment. 1066 */ 1067 if (flags & (TH_SYN|TH_FIN)) { 1068 if (flags & TH_SYN) 1069 tp->snd_nxt++; 1070 if (flags & TH_FIN) { 1071 tp->snd_nxt++; 1072 tp->t_flags |= TF_SENTFIN; 1073 } 1074 } 1075 if (sack_rxmit) 1076 goto timer; 1077 tp->snd_nxt += len; 1078 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1079 tp->snd_max = tp->snd_nxt; 1080 /* 1081 * Time this transmission if not a retransmission and 1082 * not currently timing anything. 1083 */ 1084 if (tp->t_rtttime == 0) { 1085 tp->t_rtttime = ticks; 1086 tp->t_rtseq = startseq; 1087 TCPSTAT_INC(tcps_segstimed); 1088 } 1089 } 1090 1091 /* 1092 * Set retransmit timer if not currently set, 1093 * and not doing a pure ack or a keep-alive probe. 1094 * Initial value for retransmit timer is smoothed 1095 * round-trip time + 2 * round-trip time variance. 1096 * Initialize shift counter which is used for backoff 1097 * of retransmit time. 1098 */ 1099 timer: 1100 if (!tcp_timer_active(tp, TT_REXMT) && 1101 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1102 (tp->snd_nxt != tp->snd_una))) { 1103 if (tcp_timer_active(tp, TT_PERSIST)) { 1104 tcp_timer_activate(tp, TT_PERSIST, 0); 1105 tp->t_rxtshift = 0; 1106 } 1107 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1108 } 1109 } else { 1110 /* 1111 * Persist case, update snd_max but since we are in 1112 * persist mode (no window) we do not update snd_nxt. 1113 */ 1114 int xlen = len; 1115 if (flags & TH_SYN) 1116 ++xlen; 1117 if (flags & TH_FIN) { 1118 ++xlen; 1119 tp->t_flags |= TF_SENTFIN; 1120 } 1121 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1122 tp->snd_max = tp->snd_nxt + len; 1123 } 1124 1125 #ifdef TCPDEBUG 1126 /* 1127 * Trace. 1128 */ 1129 if (so->so_options & SO_DEBUG) { 1130 u_short save = 0; 1131 #ifdef INET6 1132 if (!isipv6) 1133 #endif 1134 { 1135 save = ipov->ih_len; 1136 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1137 } 1138 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1139 #ifdef INET6 1140 if (!isipv6) 1141 #endif 1142 ipov->ih_len = save; 1143 } 1144 #endif 1145 1146 /* 1147 * Fill in IP length and desired time to live and 1148 * send to IP level. There should be a better way 1149 * to handle ttl and tos; we could keep them in 1150 * the template, but need a way to checksum without them. 1151 */ 1152 /* 1153 * m->m_pkthdr.len should have been set before cksum calcuration, 1154 * because in6_cksum() need it. 1155 */ 1156 #ifdef INET6 1157 if (isipv6) { 1158 /* 1159 * we separately set hoplimit for every segment, since the 1160 * user might want to change the value via setsockopt. 1161 * Also, desired default hop limit might be changed via 1162 * Neighbor Discovery. 1163 */ 1164 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1165 1166 /* TODO: IPv6 IP6TOS_ECT bit on */ 1167 error = ip6_output(m, 1168 tp->t_inpcb->in6p_outputopts, NULL, 1169 ((so->so_options & SO_DONTROUTE) ? 1170 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1171 } else 1172 #endif /* INET6 */ 1173 { 1174 ip->ip_len = m->m_pkthdr.len; 1175 #ifdef INET6 1176 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1177 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1178 #endif /* INET6 */ 1179 /* 1180 * If we do path MTU discovery, then we set DF on every packet. 1181 * This might not be the best thing to do according to RFC3390 1182 * Section 2. However the tcp hostcache migitates the problem 1183 * so it affects only the first tcp connection with a host. 1184 */ 1185 if (V_path_mtu_discovery) 1186 ip->ip_off |= IP_DF; 1187 1188 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1189 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1190 tp->t_inpcb); 1191 } 1192 if (error) { 1193 1194 /* 1195 * We know that the packet was lost, so back out the 1196 * sequence number advance, if any. 1197 * 1198 * If the error is EPERM the packet got blocked by the 1199 * local firewall. Normally we should terminate the 1200 * connection but the blocking may have been spurious 1201 * due to a firewall reconfiguration cycle. So we treat 1202 * it like a packet loss and let the retransmit timer and 1203 * timeouts do their work over time. 1204 * XXX: It is a POLA question whether calling tcp_drop right 1205 * away would be the really correct behavior instead. 1206 */ 1207 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1208 !tcp_timer_active(tp, TT_PERSIST)) && 1209 ((flags & TH_SYN) == 0) && 1210 (error != EPERM)) { 1211 if (sack_rxmit) { 1212 p->rxmit -= len; 1213 tp->sackhint.sack_bytes_rexmit -= len; 1214 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1215 ("sackhint bytes rtx >= 0")); 1216 } else 1217 tp->snd_nxt -= len; 1218 } 1219 out: 1220 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1221 switch (error) { 1222 case EPERM: 1223 tp->t_softerror = error; 1224 return (error); 1225 case ENOBUFS: 1226 if (!tcp_timer_active(tp, TT_REXMT) && 1227 !tcp_timer_active(tp, TT_PERSIST)) 1228 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1229 tp->snd_cwnd = tp->t_maxseg; 1230 return (0); 1231 case EMSGSIZE: 1232 /* 1233 * For some reason the interface we used initially 1234 * to send segments changed to another or lowered 1235 * its MTU. 1236 * 1237 * tcp_mtudisc() will find out the new MTU and as 1238 * its last action, initiate retransmission, so it 1239 * is important to not do so here. 1240 * 1241 * If TSO was active we either got an interface 1242 * without TSO capabilits or TSO was turned off. 1243 * Disable it for this connection as too and 1244 * immediatly retry with MSS sized segments generated 1245 * by this function. 1246 */ 1247 if (tso) 1248 tp->t_flags &= ~TF_TSO; 1249 tcp_mtudisc(tp->t_inpcb, 0); 1250 return (0); 1251 case EHOSTDOWN: 1252 case EHOSTUNREACH: 1253 case ENETDOWN: 1254 case ENETUNREACH: 1255 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1256 tp->t_softerror = error; 1257 return (0); 1258 } 1259 /* FALLTHROUGH */ 1260 default: 1261 return (error); 1262 } 1263 } 1264 TCPSTAT_INC(tcps_sndtotal); 1265 1266 /* 1267 * Data sent (as far as we can tell). 1268 * If this advertises a larger window than any other segment, 1269 * then remember the size of the advertised window. 1270 * Any pending ACK has now been sent. 1271 */ 1272 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1273 tp->rcv_adv = tp->rcv_nxt + recwin; 1274 tp->last_ack_sent = tp->rcv_nxt; 1275 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1276 if (tcp_timer_active(tp, TT_DELACK)) 1277 tcp_timer_activate(tp, TT_DELACK, 0); 1278 #if 0 1279 /* 1280 * This completely breaks TCP if newreno is turned on. What happens 1281 * is that if delayed-acks are turned on on the receiver, this code 1282 * on the transmitter effectively destroys the TCP window, forcing 1283 * it to four packets (1.5Kx4 = 6K window). 1284 */ 1285 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1286 goto again; 1287 #endif 1288 if (sendalot) 1289 goto again; 1290 return (0); 1291 } 1292 1293 void 1294 tcp_setpersist(struct tcpcb *tp) 1295 { 1296 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1297 int tt; 1298 1299 if (tcp_timer_active(tp, TT_REXMT)) 1300 panic("tcp_setpersist: retransmit pending"); 1301 /* 1302 * Start/restart persistance timer. 1303 */ 1304 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1305 TCPTV_PERSMIN, TCPTV_PERSMAX); 1306 tcp_timer_activate(tp, TT_PERSIST, tt); 1307 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1308 tp->t_rxtshift++; 1309 } 1310 1311 /* 1312 * Insert TCP options according to the supplied parameters to the place 1313 * optp in a consistent way. Can handle unaligned destinations. 1314 * 1315 * The order of the option processing is crucial for optimal packing and 1316 * alignment for the scarce option space. 1317 * 1318 * The optimal order for a SYN/SYN-ACK segment is: 1319 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1320 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1321 * 1322 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1323 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1324 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1325 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1326 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1327 */ 1328 int 1329 tcp_addoptions(struct tcpopt *to, u_char *optp) 1330 { 1331 INIT_VNET_INET(curvnet); 1332 u_int mask, optlen = 0; 1333 1334 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1335 if ((to->to_flags & mask) != mask) 1336 continue; 1337 if (optlen == TCP_MAXOLEN) 1338 break; 1339 switch (to->to_flags & mask) { 1340 case TOF_MSS: 1341 while (optlen % 4) { 1342 optlen += TCPOLEN_NOP; 1343 *optp++ = TCPOPT_NOP; 1344 } 1345 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1346 continue; 1347 optlen += TCPOLEN_MAXSEG; 1348 *optp++ = TCPOPT_MAXSEG; 1349 *optp++ = TCPOLEN_MAXSEG; 1350 to->to_mss = htons(to->to_mss); 1351 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1352 optp += sizeof(to->to_mss); 1353 break; 1354 case TOF_SCALE: 1355 while (!optlen || optlen % 2 != 1) { 1356 optlen += TCPOLEN_NOP; 1357 *optp++ = TCPOPT_NOP; 1358 } 1359 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1360 continue; 1361 optlen += TCPOLEN_WINDOW; 1362 *optp++ = TCPOPT_WINDOW; 1363 *optp++ = TCPOLEN_WINDOW; 1364 *optp++ = to->to_wscale; 1365 break; 1366 case TOF_SACKPERM: 1367 while (optlen % 2) { 1368 optlen += TCPOLEN_NOP; 1369 *optp++ = TCPOPT_NOP; 1370 } 1371 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1372 continue; 1373 optlen += TCPOLEN_SACK_PERMITTED; 1374 *optp++ = TCPOPT_SACK_PERMITTED; 1375 *optp++ = TCPOLEN_SACK_PERMITTED; 1376 break; 1377 case TOF_TS: 1378 while (!optlen || optlen % 4 != 2) { 1379 optlen += TCPOLEN_NOP; 1380 *optp++ = TCPOPT_NOP; 1381 } 1382 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1383 continue; 1384 optlen += TCPOLEN_TIMESTAMP; 1385 *optp++ = TCPOPT_TIMESTAMP; 1386 *optp++ = TCPOLEN_TIMESTAMP; 1387 to->to_tsval = htonl(to->to_tsval); 1388 to->to_tsecr = htonl(to->to_tsecr); 1389 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1390 optp += sizeof(to->to_tsval); 1391 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1392 optp += sizeof(to->to_tsecr); 1393 break; 1394 case TOF_SIGNATURE: 1395 { 1396 int siglen = TCPOLEN_SIGNATURE - 2; 1397 1398 while (!optlen || optlen % 4 != 2) { 1399 optlen += TCPOLEN_NOP; 1400 *optp++ = TCPOPT_NOP; 1401 } 1402 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1403 continue; 1404 optlen += TCPOLEN_SIGNATURE; 1405 *optp++ = TCPOPT_SIGNATURE; 1406 *optp++ = TCPOLEN_SIGNATURE; 1407 to->to_signature = optp; 1408 while (siglen--) 1409 *optp++ = 0; 1410 break; 1411 } 1412 case TOF_SACK: 1413 { 1414 int sackblks = 0; 1415 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1416 tcp_seq sack_seq; 1417 1418 while (!optlen || optlen % 4 != 2) { 1419 optlen += TCPOLEN_NOP; 1420 *optp++ = TCPOPT_NOP; 1421 } 1422 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1423 continue; 1424 optlen += TCPOLEN_SACKHDR; 1425 *optp++ = TCPOPT_SACK; 1426 sackblks = min(to->to_nsacks, 1427 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1428 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1429 while (sackblks--) { 1430 sack_seq = htonl(sack->start); 1431 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1432 optp += sizeof(sack_seq); 1433 sack_seq = htonl(sack->end); 1434 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1435 optp += sizeof(sack_seq); 1436 optlen += TCPOLEN_SACK; 1437 sack++; 1438 } 1439 TCPSTAT_INC(tcps_sack_send_blocks); 1440 break; 1441 } 1442 default: 1443 panic("%s: unknown TCP option type", __func__); 1444 break; 1445 } 1446 } 1447 1448 /* Terminate and pad TCP options to a 4 byte boundary. */ 1449 if (optlen % 4) { 1450 optlen += TCPOLEN_EOL; 1451 *optp++ = TCPOPT_EOL; 1452 } 1453 /* 1454 * According to RFC 793 (STD0007): 1455 * "The content of the header beyond the End-of-Option option 1456 * must be header padding (i.e., zero)." 1457 * and later: "The padding is composed of zeros." 1458 */ 1459 while (optlen % 4) { 1460 optlen += TCPOLEN_PAD; 1461 *optp++ = TCPOPT_PAD; 1462 } 1463 1464 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1465 return (optlen); 1466 } 1467